In an LTE cellular network, the User Equipment (UE), such as a cellular phone or wireless handheld computing device, attaches to a base station of a cell by repeated requests (preambles) on the Random Access Channel until the request is acknowledged. The successful conclusion of this sequence is known as “UE attach”.
The number of requests needed per UE attach is an important characteristic of an LTE cell. If this number of requests is high, this indicates lengthy delays in attaching, due to congestion in the cell or a badly-configured cell.
When the User Equipment successfully attaches to the base station (such as an evolution node B, eNodeB or eNB for the LTE examples) of the cell of the network, the UE sends the counter numberOfPreamblesSent to the eNB, to inform the eNB how many attempts had been made before success. This is set out in 3GPP specification 32.331 clause 6.2.2.
To make a decision about the performance of the network, information about each cell must be transferred to a management system. It is not practical to transfer the numberOfPreamblesSent counter for each UE attach. In a large network, there could be several millions of UE attaches per hour.